CN104682748A - Photovoltaic grid-connected inverter space voltage vector double hysteresis current control method and system - Google Patents

Abstract

The invention discloses a photovoltaic grid-connected inverter space voltage vector double hysteresis current control method and system. The line current is subjected to decoupling control by utilizing the relationship between the line current and the power device on-off state of a photovoltaic grid-connected inverter, the reference space voltage vector position is detected by utilizing the double hysteresis, a PLL (phase locked loop) circuit is combined for detecting the output switching value, and the frequency closed-loop control is formed. The method and the system have the advantages that on the basis of maintaining the advantages of high current response speed, certain current limiting capability and the like of the traditional hysteresis control, the constant on-off frequency of a power device can effectively maintained, the on-off loss of the power device is reduced, the design of a driving circuit and a protecting circuit is favorably realized, and good practical application values are realized.

Description

Photovoltaic combining inverter space voltage vector Double hysteresis current control method and system

Technical field

The invention belongs to photovoltaic combining inverter and control technology field thereof, specifically a kind of photovoltaic combining inverter space voltage vector Double hysteresis current control method and system.

Background technology

Energy shortage is the significant problem that the world today faces, significant to the research in renewable energy power generation field.As the key equipment of photovoltaic power generation technology, the research of photovoltaic combining inverter and control technology thereof is more and more subject to common concern.

At present, what major part photovoltaic DC-to-AC converter adopted is three-phase half-bridge voltage type inverter topology, control mode mostly is Controlled in Current Mode and Based, such as hysteretic loop current control, hysteretic loop current control has good current tracking performance, but because ring width is constant, the switching frequency excursion that will cause power device is comparatively large, the series of problems such as cause AC filter inductance difficult design and power model stress and switching loss larger.

Ask that the Double hysteresis current control strategy of voltage vector proposes for the shortcoming of the stagnant ring of conventional current based on sky, its cardinal principle is by regulating Hysteresis Current width to maintain the substantially constant of switching frequency in real time.With regard on the realization means of this principle, the research of some scholars at present, can be divided into following three aspects.

(1) utilize PLL circuit to form switching frequency closed loop controller, the fixing square-wave signal of switching signal and given frequency is compared, and the phase difference value be given to regulates the ring width value obtaining expectation through PI.This method can make the phase difference of output voltage pulse train and clock pulse sequence minimally effectively.

(2) hysteresis band current error predicted method is adopted, by the sampling to (K-1) T moment current error, dope the variation tendency of KT moment current error, and calculate the switching over moment in next cycle, within given cycle, complete the on/off of a brachium pontis switch, it is frequently fixed to realize.This method can realize Digital Control, but the real-time amount of calculation of controller is very large, and Inductor and choosing of resistance parameter affect larger on electric current low-order harmonic content.

(3) utilize two stagnant ring to realize fixed-frequency hysteresis SVPWM, the method adopts two stagnant ring comparing unit, and the effect of interior stagnant ring comparing unit determines that sky asks voltage reference vector, and outer stagnant ring comparing unit exports final on off state value.This method key is that sky asks voltage reference vector V ^*determination.Because this control method combines SVPWM modulation, effectively improve voltage utilization.

In addition; document " Wang Defa; Ding Hongfa. based on dynamic electric voltage recovery device research [J] of little symmetrical cascade type multi-electrical level inverter. protecting electrical power system and control; 2007; 35 (13): 49-52,60. " propose a kind of fixed-frequency hysteresis control algolithm that can be applicable to single-phase inverter.The present invention, on the basis of document conclusion, is incorporated into three-phase this algorithm and is also improved without in center line inverter structure, finally in Matlab, carry out simulating, verifying, demonstrate the feasibility of this innovatory algorithm.

Summary of the invention

The object of the present invention is to provide a kind of photovoltaic combining inverter space voltage vector Double hysteresis current control method and system, to solve the problem proposed in above-mentioned background technology.

For achieving the above object, the invention provides following technical scheme:

A kind of photovoltaic combining inverter space voltage vector Double hysteresis current control method, utilize the relation of photovoltaic combining inverter line current and power device on off state, uneoupled control is carried out to line current, two stagnant ring is utilized to detect with reference to empty position of asking voltage vector, in conjunction with PLL circuit, output switch amount is detected, form Frequency servo.

As the further scheme of the present invention: carry out uneoupled control to line current and adopt three-phase without center line inverter line current solution lotus root algorithm.

As the further scheme of the present invention: described three-phase is utilize a phase on off state and i without center line inverter line current solution lotus root algorithm _bcirrelevant, i.e. a phase on off state and line current i _beseparate lotus root algorithm, to i _ab, i _bc, i _cacarry out and separate lotus root control, △ i _ab, △ i _bc, △ i _caas the input of current hysteresis-band control device, realize fixed-frequency control in conjunction with SVPWM modulation system and PLL phase-detection.

As the further scheme of the present invention: utilize two stagnant ring to detect and ask that the position of voltage vector adopts SVPWM and two block ring regulation algorithm with reference to empty.

As the further scheme of the present invention: described SVPWM and two block ring regulation algorithm are the theories utilizing voltage sky to ask vector, outer stagnant ring is used for differentiating the parallelogram position at reference voltage place, interior stagnant ring effect is the quadrangle positional information according to determining, determine the final control voltage vector adopted, finally determine threephase switch function S by two hysteresis comparator _a, S _b, S _cproblems of value.

As the further scheme of the present invention: the effect of interior stagnant ring is exactly to reference voltage vector u ^*four voltage control vectors of the quadrilateral area at place are selected.

As the further scheme of the present invention: stagnant ring does in the process of line current error-detecting outside, utilize phase-locked loop circuit to carry out phase control to two corresponding controlled line current errors, make these two current error phase places contrary.

As the further scheme of the present invention: utilize Matlab/Simulink tool box and 3kW experiment porch to carry out experimental verification to two Hysteresis control algorithm.

A kind of system adopting described photovoltaic combining inverter space voltage vector Double hysteresis current control method.

Compared with prior art, the invention has the beneficial effects as follows:

The present invention is according to the relation of inverter line current and power device on off state, line current is carried out and separates lotus root control, utilize two stagnant ring to judge the position of reference space voltage vector, in conjunction with phase-locked loop circuit, the on off state stolen out is detected, form Frequency servo.Matlab/Simulink tool box and 3kW experiment porch is finally utilized to verify two Hysteresis control algorithm.Result shows, this algorithm remains that the response of traditional Hysteresis control current tracking is fast, the advantage of current limiting ability, also effectively overcomes that switching frequency change is fixing, the switching loss problem such as greatly simultaneously.

Accompanying drawing explanation

Fig. 1 is the current hysteresis-band control structure chart of three-phase photovoltaic grid-connected inverting device.

Fig. 2 is the circuit diagram of a phase brachium pontis main circuit.

Fig. 3 is the graph of a relation of the stagnant ring of a phase current and error current.

Fig. 4 is that three-phase is without center line converter main circuit topology figure.

Fig. 5 is state vector division figure in the plane.

Fig. 6 is two Hysteresis control structured flowcharts.

Fig. 7 is the three-phase grid-connected inverter a phase phase voltage Ea and the phase current i that adopt voltage sky to ask vector Double hysteresis current control algorithm _aoscillogram.

Fig. 8 is inverter triple line current i _ab, i _bc, i _caoscillogram.

Fig. 9 is line current i _aberror current oscillogram.

Figure 10 is the three-phase grid-connected inverter output current i when being 6kHz to constant switching frequency _aexperimental waveform figure.

Figure 11 is the three-phase grid-connected inverter output current i when being 10kHz to constant switching frequency _aexperimental waveform figure.

Figure 12 be given switching frequency at 6kHz time a phase brachium pontis PWM output waveform figure.

Figure 13 be given switching frequency at 10kHz time a phase brachium pontis PWM output waveform figure.

Embodiment

Be described in more detail below in conjunction with the technical scheme of embodiment to this patent.

In order to understand photovoltaic combining inverter space voltage vector Double hysteresis current control method and system further, first the functional relation of hysteresis band and switching frequency is described in detail below.

Figure 1 shows that the current hysteresis-band control structure chart of three-phase photovoltaic grid-connected inverting device, its general principle is that feedback current and given electric current are compared, △ i is as the input of hysteresis comparator, making actual input current do zigzag tracking change around given current signal by setting rational hysteresis band, reaching the object of tracing preset electric current.The fixing meeting of Hysteresis Current width causes power device switching frequency non-constant, causes power device switching loss excessive, and this requires higher to Drive Protecting Circuit hardware designs.

In order to switching frequency f is described _sand the functional relation between hysteresis band h, now analyze with a phase brachium pontis frequency change, as shown in Figure 2, main circuit current voltage relationship is a phase brachium pontis main circuit topology:

$u_a={\mathrm{Ri}}_a+L\frac{{\mathrm{di}}_a}{\mathrm{dt}}+e_a---\left(1\right)$

Wherein: e _afor AC electrical network electromotive force; L, R are respectively Inductor and resistance; i _arepresent a phase current.

Fig. 3 is the graph of a relation of the stagnant ring of a phase current and error current, ignores the impact of converter resistance drop, and formula (1) can be expressed as:

$\frac{{\mathrm{di}}_a}{\mathrm{dt}}=\frac{u_a-e_a}{L}---\left(2\right)$

Because inverter switching frequency is higher, therefore, in a switch periods T, linearization process can be carried out to output voltage values, assuming that ask that when △ t internal inductance current error value is △ i _a, then formula (2) can be rewritten as:

$\mathrm{\Δt}=\frac{\mathrm{\ΔiL}}{u_a-e_a}---\left(3\right)$

Make switch periods T=t ₁+ t ₂, ask during segmentation that function can be expressed as:

$\left\{\begin{array}{c}{t}_1=\frac{2\mathrm{hL}}{\frac{u_{\mathrm{dc}}}{2}-e_a}(u_a=\frac{u_{\mathrm{dc}}}{2},\mathrm{\Δ}{i}_a=2h)\\ t_2=\frac{-2\mathrm{hL}}{-\frac{u_{\mathrm{dc}}}{2}-e_a}(u_a=\frac{u_{\mathrm{dc}}}{2},\mathrm{\Δ}{i}_a=-2h)\end{array}\right.---\left(4\right)$

Composite type (3) and formula (4), the functional relation obtained between Hysteresis Current width and switching frequency is:

$h=\frac{{\left(\frac{u_{\mathrm{dc}}}{2}\right)}^2-{e_a}^2}{2f_{s}L{u}_{\mathrm{dc}}}---\left(5\right)$

As can be seen from formula (5), hysteresis band is switching frequency f _s, filter inductance L, DC side output voltage u _dc, AC electrical network electromotive force e _afunction because L immobilizes, as long as so keep h and u _dc, e _aaccording to the change of certain functional relation, just can maintained switch frequency f _sconstant.

A kind of photovoltaic combining inverter space voltage vector Double hysteresis current control method that the present invention proposes, comprises (1) three-phase without center line inverter line current solution lotus root algorithm and (2) SVPWM and two block ring regulation algorithm.Be described in detail below.

(1) three-phase is without center line inverter line current solution lotus root algorithm

Based on triple line solution for the current lotus root algorithm, utilize a phase on off state and i _bcirrelevant, i.e. a phase on off state and line current i _beseparate lotus root algorithm, to i _ab, i _bc, i _cacarry out and separate lotus root control, △ i _ab, △ i _bc, △ i _caas the input of current hysteresis-band control device, realize fixed-frequency control in conjunction with SVPWM modulation system and PLL phase-detection.

Fig. 4 be three-phase without center line converter main circuit topology figure, now a phase bridge arm voltage equation is no longer formula (1), should be written as:

$u_{\mathrm{aN}}=e_a-{\mathrm{Ri}}_a-L\frac{{\mathrm{di}}_a}{\mathrm{dt}}-u_{\mathrm{NO}}---\left(6\right)$

Wherein: u _aNrepresent the output voltage of the relative N point of a phase; e _arepresent AC electrical network electromotive force; i _arepresent a cross streams electric current.

Formula (6) shows, owing to there is mid-point voltage U _nO, simultaneously again because U _nOchange by the change of each phase power switch pipe on off state, therefore the change of each phase current is all by the impact of other two-phase on off state, namely there is misfortune conjunction between three-phase current, can not the conclusion of wushu (5) directly be used.Want to realize the independent control to each phase current, need to carry out solution lotus root to AC line current.

For a phase, switch function still adopts binary states to control, and ignores the ohmically pressure drop of AC, and formula (6) can be rewritten as:

$u_{\mathrm{ao}}=e_a+L\frac{{\mathrm{di}}_a}{\mathrm{dt}}---\left(7\right)$

As Sa=0, the line voltage between a, b can be expressed as:

u _ab＝u _aN-u _bN＝(s _a-s _b)u _dc＝-s _bu _dc(8)

Between a, b, the error equation of line current is:

$L\frac{\mathrm{d\Δ}{i}_{\mathrm{ab}}}{\mathrm{dt}}=u_{\mathrm{ab}}^{*}-u_{\mathrm{ab}}=u_{\mathrm{ab}}^{*}+s_b{u}_{\mathrm{dc}}---\left(9\right)$

As can be seen from formula (9), because Sa=0 determines, u _absize can by s _bcontrol, i.e. △ i _abalso by s _bcontrol.S in the process _cnot to △ i _abchange have an impact, i.e. △ i _absize have nothing to do with c phase.Line voltage between a, c can be expressed as:

u _ca＝u _cN-u _aN＝(s _c-s _a)u _dc＝s _cu _dc(10)

The error equation of a, c line current is:

$L\frac{\mathrm{d\Δ}{i}_{\mathrm{ca}}}{\mathrm{dt}}=u_{\mathrm{ca}}^{*}-u_{\mathrm{ca}}=u_{\mathrm{ca}}^{*}+s_c{u}_{\mathrm{dc}}---\left(11\right)$

Equally, △ i _caand u _cavalue also only by s _cdetermine, with s _birrelevant.

That more than analyze is s _awhen=0, s _band s _cfunction is respectively to line current i _ab, i _cacontrol action.In like manner, at s _b=0 and s _cin=0 two kind of situation, analyze other two-phase switch functions to the impact of line current and s _aanalytic process in=0 situation is consistent.What table 1 represented is the control planning of each switching value to line current.

The control planning of table 1 switch function and line current

(2) SVPWM and two block ring regulation algorithm

Utilize voltage sky to ask the theory of vector, under binary states modulation, above-mentioned each phase switch function can represent with table 2 control action of inverter side voltage vector.

The relation of table 2 switch function and voltage

s a	s b	s c	U aN	U bN	U cN	U ab	U bc	U ca	U K
										0	0	0	0	0	0	0	0	0	U 0
1	0	0	U dc	0	0	U dc	0	-U dc	U 1
										1	1	0	U dc	U dc	0	0	U dc	-U dc	U 2
0	1	0	0	U dc	0	-U dc	U dc	0	U 3
										0	1	1	0	U dc	U dc	-U dc	0	U dc	U 4
0	0	1	0	0	U dc	0	-U dc	U dc	U 5
										1	0	1	U dc	0	U dc	U dc	-U dc	0	U 6
1	1	1	U dc	U dc	U dc	0	0	0	U 7

Associative list 1 and table 2 can be found out, the hexagon that six nonzero voltage space vectors surround can be divided into three parts, and Fig. 5 is state vector division figure in the plane, and three parallelogram that wherein dotted line surrounds represent s respectively _a=0, s _b=0 and s _cthe region of=0.With s _athe quadrangle (III-IV) at=0 place is example, and the now lower brachium pontis conducting all the time of a phase, during the change of b phase switch function, voltage vector is all the time at (U0, U ₃) or (U ₄, U ₅) between mutually switch, △ i _abonly control by b phase switch function; During the change of c phase switch function, voltage vector will at (U0, U ₅) or (U ₃, U ₄) between mutually switch, △ i _caonly control by c phase switch function.Table 3 lists the vector corresponding relation between each switch function and parallelogram.

The corresponding relation of table 3 switch function and quadrangle

s i	s ab	s bc	s ca	Vector contained by parallelogram
					s a＝0	0	*	1	U 0，U 3，U 4，U 5
s b＝0	1	0	*	U 0，U 1，U 2，U 3
					s c＝0	*	1	0	U 0，U 1，U 5，U 6

The control objectives of line current solution misfortune algorithm is current error △ i _ab, △ i _bc, △ i _ca, committed step is the detection to reference voltage vector u* position.

As can be seen from Table 3, for each parallelogram, reference voltage vector can only synthesize by the voltage vector contained by quadrangle, therefore, wants the position detecting u* place, first can detect the parallelogram at u* place, the present invention adopt document " Yang Xu, Wang Zhaoan. a kind of accurate fixed frequency stagnant ring PWM current control method [J] electrotechnics journal newly, 2003; 18 (3): 24-28. " in method, utilize two stagnant ring to detect reference voltage vector u*.Roughly thinking is: outer stagnant ring is used for differentiating the parallelogram position at reference voltage place, and interior stagnant ring effect is the quadrangle positional information according to determining, determines the final control voltage vector adopted.

With regard to outer Hysteresis control, it is input as △ i _ab, △ i _bc, △ i _ca, export as S _ab, S _bc, S _ca, work as S _abwhen=1, explanation should apply command voltage u* _ab, make i _abincrease, work as S _abwhen=0, i should be made _abincrease.If now outer stagnant ring exports and meets S _ab=1, S _bc=0, then description references voltage vector u* is in S _bthe quadrilateral area of=0, namely the position of u* can be determined.

The effect of interior stagnant ring is exactly select four voltage control vectors of the quadrilateral area at reference voltage vector u* place.

With S _athe parallelogram of=1 correspondence is example, and now outer stagnant ring exports as S _ab=0, S _ca=1, according to formula (10) and formula (11) known, the lower brachium pontis of b phase and brachium pontis conducting all the time in c phase, i.e. S _b=0, S _c=1, d Δ i _ab/ dt>0, d Δ i _ca/ dt<0, △ i _abincrease, d Δ i _careduce.Again because meet d Δ i between error current _bc=-(d Δ i _ab+ d Δ i _ca) relation, therefore inner ring control in, △ i should be kept as far as possible _abwith △ i _casize is close, and phase place is contrary, to reduce △ i _bcfor two error current △ i _abwith △ i _ca, be not difficult to find out from Fig. 3, it is consistent that peak point moment and switch function due to error current change the moment, as long as therefore can ensure △ i _abwith △ i _caphase place contrary, just can realize △ i _bcminimum.Carry out logical operation according to formula (9)-(11), interior stagnant ring can be obtained and export the logical relation with switch function:

$\left\{\begin{array}{c}{s}_a=s_{\mathrm{bc}}\&CenterDot;{\stackrel{\&OverBar;}{s}}_{\mathrm{ca}}\&CenterDot;s_{\mathrm{ca}}^{\&prime;}+s_{\mathrm{ab}}\&CenterDot;{\stackrel{\&OverBar;}{s}}_{\mathrm{bc}}\&CenterDot;s_{\mathrm{ab}}^{\&prime;}\\ s_b=s_{\mathrm{ca}}\&CenterDot;{\stackrel{\&OverBar;}{s}}_{\mathrm{ab}}\&CenterDot;{\stackrel{\&OverBar;}{s}}_{\mathrm{ab}}^{\&prime;}+s_{\mathrm{bc}}\&CenterDot;s_{\mathrm{ca}}\&CenterDot;s_{\mathrm{bc}}^{\&prime;}\\ s_c=s_{\mathrm{ab}}\&CenterDot;{\stackrel{\&OverBar;}{s}}_{\mathrm{bc}}\&CenterDot;{\stackrel{\&OverBar;}{s}}_{\mathrm{bc}}^{\&prime;}+s_{\mathrm{ca}}\&CenterDot;{\stackrel{\&OverBar;}{s}}_{\mathrm{ab}}\&CenterDot;s_{\mathrm{ca}}^{\&prime;}\end{array}\right.---\left(12\right)$

Wherein: S _ab, S _bc, S _ca, represent outer stagnant ring output state value; S ' _ab, S ' _bc, S ' _ca, stagnant ring output state value in representing.

Obviously, threephase switch function S is finally determined by two hysteresis comparator _a, S _b, S _cproblems of value.In addition, stagnant ring does in the process of line current error-detecting outside, and need to utilize phase-locked loop circuit to carry out phase control to two corresponding controlled line current errors, make these two current error phase places contrary, Fig. 6 is final two Hysteresis control structured flowcharts.

Simulation and experiment checking is carried out to the present invention below.

Emulate two stagnant ring SVPWM algorithm, main circuit simulation parameter is: AC filter inductance 5mH, DC side load R _l=20 Ω DC bus capacitor C _dc=1000 μ F, AC equivalent resistance R=0.5 Ω, AC power supply is f=50Hz, E=380V, to constant switching frequency f _s=5kHz, simulation step length is 10 ^-6s.

Fig. 7 is the three-phase grid-connected inverter a phase phase voltage Ea and the phase current i that adopt voltage sky to ask vector Double hysteresis current control algorithm _aoscillogram; Can find out, phase current i _asine degree better, substantially maintain the phase 180 ° with phase voltage Ea, namely now inverter is in unity power factor running status.

Fig. 8 is inverter triple line current i _ab, i _bc, i _caoscillogram, when Os<t<O.15s in the section of asking, inverter is now in transient process, line current fluctuation is larger, when t>0.15s, inverter works in stable state, now line current sineization substantially.

Fig. 9 is line current i _aberror current oscillogram, its error current range stabilises, within 0.1A, embodies the trace performance that actual line electric current is good to reference line electric current.

In design power be further 3kW photovoltaic combining inverter experiment porch on carry out experimental verification research, control algolithm realizes in processor TMS320LF2812, and experimental provision major parameter is: batteries DC voltage value U _dc=300V; The magnitude of voltage that is connected to the grid is 220V, inverter bridge selects Fuji IGBT (1400V/30A) output AC side filter inductance to be 2mH, direct current grading resistor 14k Ω × 2, electric capacity of voltage regulation is 2200 μ F/400V, AC resistance 10 Ω, be 6kHz and 10kHz to constant switching frequency, PSHI2012 × 3 selected by drive circuit.In order to observe inverter AC output current wave under different switching frequency, given frequency is set respectively in 6kHz and 10kHz two groups experiment to contrast.

Figure 10 and Figure 11 is the three-phase grid-connected inverter output current i when being 6kHz and 10kHz to constant switching frequency _aexperimental waveform figure.Figure 12 and Figure 13 be given switching frequency at 6kHz and 10kHz time a phase brachium pontis PWM output waveform figure.Relatively can be found out by the current waveform of Figure 10 and Figure 11; along with the rising of switching frequency; the sineization of current waveform is better; but meanwhile; the loss of power device is also risen thus; also higher to the requirement of Drive Protecting Circuit, above-mentioned experimental waveform demonstrates the correctness of this control strategy substantially.

The present invention is at document " Wang Defa, Ding Hongfa. based on dynamic electric voltage recovery device research [J] of little symmetrical cascade type multi-electrical level inverter. protecting electrical power system and control, 2007, 35 (13): 49-52, the sky basis of 60. " conclusion proposing a kind of applicable three-phase photovoltaic grid-connected inverting device asks voltage vector Double hysteresis current control algorithm, its cardinal principle is the relation utilizing photovoltaic combining inverter line current and power device on off state, uneoupled control is carried out to line current, two stagnant ring is utilized to detect with reference to empty position of asking voltage vector, in conjunction with PLL circuit, output switch amount is detected, form Frequency servo.By asking the emulation of voltage vector Double hysteresis current control algorithm to sky, demonstrate the feasibility of this innovatory algorithm.The current response rate that this control algolithm is remaining traditional Hysteresis control is fast, have on the basis of the advantages such as certain current limiting capacity; can effectively keep power device switching frequency constant; reduce power device switching loss; contribute to the design of drive circuit and protective circuit, possess good actual application value.

Above the better embodiment of this patent is explained in detail, but this patent is not limited to above-mentioned execution mode, in the ken that one skilled in the relevant art possesses, can also makes a variety of changes under the prerequisite not departing from this patent aim.

Claims (9)

1. a photovoltaic combining inverter space voltage vector Double hysteresis current control method, it is characterized in that, utilize the relation of photovoltaic combining inverter line current and power device on off state, uneoupled control is carried out to line current, two stagnant ring is utilized to detect with reference to empty position of asking voltage vector, in conjunction with PLL circuit, output switch amount is detected, form Frequency servo.

2. photovoltaic combining inverter space voltage vector Double hysteresis current control method according to claim 1, is characterized in that, carries out uneoupled control adopt three-phase without center line inverter line current solution lotus root algorithm to line current.

3. photovoltaic combining inverter space voltage vector Double hysteresis current control method according to claim 2, is characterized in that, described three-phase is utilize a phase on off state and i without center line inverter line current solution lotus root algorithm _bcirrelevant, i.e. a phase on off state and line current i _beseparate lotus root algorithm, to i _ab, i _bc, i _cacarry out and separate lotus root control, △ i _ab, △ i _bc, △ i _caas the input of current hysteresis-band control device, realize fixed-frequency control in conjunction with SVPWM modulation system and PLL phase-detection.

4. photovoltaic combining inverter space voltage vector Double hysteresis current control method according to claim 1, is characterized in that, utilizes two stagnant ring to detect and asks that the position of voltage vector adopts SVPWM and two block ring regulation algorithm with reference to empty.

5. photovoltaic combining inverter space voltage vector Double hysteresis current control method according to claim 4, it is characterized in that, described SVPWM and two block ring regulation algorithm are the theories utilizing voltage sky to ask vector, outer stagnant ring is used for differentiating the parallelogram position at reference voltage place, interior stagnant ring effect is the quadrangle positional information according to determining, determine the final control voltage vector adopted, finally determine threephase switch function S by two hysteresis comparator _a, S _b, S _cproblems of value.

6. photovoltaic combining inverter space voltage vector Double hysteresis current control method according to claim 4, is characterized in that, the effect of interior stagnant ring is exactly to reference voltage vector u ^*four voltage control vectors of the quadrilateral area at place are selected.

7. according to the photovoltaic combining inverter space voltage vector Double hysteresis current control method one of claim 4-6 Suo Shu, it is characterized in that, stagnant ring does in the process of line current error-detecting outside, utilize phase-locked loop circuit to carry out phase control to two corresponding controlled line current errors, make these two current error phase places contrary.

8. according to the photovoltaic combining inverter space voltage vector Double hysteresis current control method one of claim 1-6 Suo Shu, it is characterized in that, utilize Matlab/Simulink tool box and 3kW experiment porch to carry out experimental verification to two Hysteresis control algorithm.

9. one kind adopts the system of photovoltaic combining inverter space voltage vector Double hysteresis current control method as described in one of claim 1-6.